Combination, method, and composition for chemical mechanical planarization of a tungsten-containing substrate

ABSTRACT

A combination, composition and associated method for chemical mechanical planarization of a tungsten-containing substrate are described herein which afford tunability of tungsten/dielectric selectivity and low selectivity for tungsten removal in relation to dielectric material. Removal rates for both tungsten and dielectric are high and stability of the slurry (e.g., with respect to pH drift over time) is high.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. applicationSer. No. 12/630,304 filed Dec. 3, 2009, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/140,216 filed Dec. 23, 2008.

BACKGROUND OF THE INVENTION

This invention relates generally to the chemical-mechanicalplanarization (CMP) of tungsten-containing substrates on semiconductorwafers and slurry compositions therefore. In particular, the presentinvention relates to a CMP slurry composition that is effective for usein tungsten CMP and which is a low tungsten/dielectric selectivityslurry for tungsten CMP that is tunable and that simultaneously affordsrelatively high removal rates of tungsten and dielectric material duringCMP processing. In some embodiments, the slurry has excellent pHstability that is virtually constant over many months This invention isespecially useful for tungsten CMP where low selectivity for tungsten todielectric removal as well as low dishing/plug recess on planarizedsubstrates is desired.

CMP for planarization of semiconductor substrates is now widely known tothose skilled in the art and has been described in numerous patents andopen literature publications. An introductory reference on CMP is asfollows: “Chemical—Mechanical Polish” by G. B. Shinn et al., Chapter 15,pages 415-460, in Handbook of Semiconductor Manufacturing Technology,editors: Y. Nishi and R. Doering, Marcel Dekker, New York City (2000).

In a typical CMP process, a substrate (e.g., a wafer) is placed incontact with a rotating polishing pad attached to a platen. A CMPslurry, typically an abrasive and chemically reactive mixture, issupplied to the pad during CMP processing of the substrate. During theCMP process, the pad (fixed to the platen) and substrate are rotatedwhile a wafer carrier system or polishing head applies pressure(downward force) against the substrate. The slurry accomplishes theplanarization (polishing) process by chemically and mechanicallyinteracting with the substrate film being planarized due to the effectof the rotational movement of the pad relative to the substrate.Polishing is continued in this manner until the desired film on thesubstrate is removed with the usual objective being to effectivelyplanarize the substrate. Typically metal CMP slurries contain anabrasive material, such as silica or alumina, suspended in an oxidizing,aqueous medium.

There are a large number of materials used in the manufacture ofintegrated circuits such as a semiconductor wafer. The materialsgenerally fall into three categories—dielectric material, adhesionand/or barrier layers, and conductive layers. The use of the varioussubstrates, e.g., dielectric material such as tetraethylorthosilicate(TEOS), plasma enhanced tetraethylorthosilicate (PETEOS), and low-kdielectric materials; barrier/adhesion layers such as tantalum,titanium, tantalum nitride, and titanium nitride; and conductive layerssuch as copper, aluminum, tungsten, and noble metals is known in theindustry.

Integrated circuits are interconnected through the use of well-knownmultilevel interconnections. Interconnection structures normally have afirst layer of metallization, an interconnection layer, a second levelof metallization, and typically third and subsequent levels ofmetallization. Inter-level dielectric materials such as silicon dioxideand sometimes low-k materials are used to electrically isolate thedifferent levels of metallization in a silicon substrate or well. Theelectrical connections between different interconnection levels are madethrough the use of metallized vias and in particular tungsten vias.Methods are known for preparing multiple metallized layers andmetallized vias in insulator films. In a similar manner, metal contactsare used to form electrical connections between interconnection levelsand devices formed in a well. The metal vias and contacts are generallyfilled with tungsten and generally employ an adhesion layer such astitanium nitride (TiN) and/or titanium to adhere a metal layer such as atungsten metal layer to the dielectric material.

In one semiconductor manufacturing process, metallized vias or contactsare formed by a blanket tungsten deposition followed by a CMP step. In atypical process, via holes are etched through the inter-level dielectric(ILD) to interconnection lines or to a semiconductor substrate. Next, athin adhesion layer such as titanium nitride and/or titanium isgenerally formed over the ILD and is directed into the etched via hole.Then, a tungsten film is blanket deposited over the adhesion layer andinto the via. The deposition is continued until the via hole is filledwith tungsten. Finally, the excess tungsten is removed by chemicalmechanical polishing (CMP) to form metal vias.

The ratio of the removal rate of a metal (e.g., tungsten) to the removalrate of a dielectric base is called the “selectivity” for removal of themetal in relation to removal of the dielectric during CMP processing ofsubstrates comprised of metal and dielectric material. When CMP slurrieswith high selectivity for removal of metal in relation to dielectric areused, the metal layers are easily over-polished creating a depression or“dishing” effect in the metalized areas. This feature distortion isunacceptable due to lithographic and other constraints in semiconductormanufacturing.

Another feature distortion that is unsuitable for semiconductormanufacturing is called “erosion.” Erosion is the topography differencebetween a field of dielectric and a dense array of metal vias ortrenches. In CMP, the materials in the dense array maybe removed oreroded at a faster rate than the surrounding field of dielectric. Thiscauses a topography difference between the field of dielectric and thedense metal (e.g., copper or tungsten) array.

As industry standards trend toward smaller device features, there is anever-developing need for CMP slurries that deliver superiorplanarization of the nanostructures of integrated circuit (IC) chips.Specifically, for 45 nm (nanometer) technology nodes and smaller featuresizes, slurry products must deliver low removal rate selectivity betweenmetal and dielectric, thereby lowering erosion while maintainingsufficient removal rate and defect levels. Furthermore, in thecompetitive market of CMP consumables, low cost of ownership (CoO),specifically through concentration of CMP slurry, is quickly becoming anindustry standard.

A typically used CMP slurry has two actions, a chemical component and amechanical component. An important consideration in slurry selection is“passive etch rate.” The passive etch rate is the rate at which a metal(e.g., copper) is dissolved by the chemical component alone and shouldbe significantly lower than the removal rate when both the chemicalcomponent and the mechanical component are involved. A large passiveetch rate leads to dishing of the metallic trenches and vias, and thus,preferably, the passive etch rate is less than 10 nanometers per minute.

These are two general types of layers that can be polished. The firstlayer is ILD, such as silicon oxide and silicon nitride. The secondlayer is metal layers, such as tungsten, copper, aluminum, etc., whichare used to connect the active devices.

In the case of CMP of metals, the chemical action is generallyconsidered to take one of two forms. In the first mechanism, thechemicals in the solution react with the metal layer to continuouslyform an oxide layer on the surface of the metal. This generally requiresthe addition of an oxidizer to the solution such as hydrogen peroxide,ferric nitrate, etc. Then the mechanical abrasive action of theparticles continuously and simultaneously removes this oxide layer. Ajudicious balance of these two processes obtains optimum results interms of removal rate and polished surface quality.

In the second mechanism, no protective oxide layer is formed. Instead,the constituents in the solution chemically attack and dissolve themetal, while the mechanical action is largely one of mechanicallyenhancing the dissolution rate by such processes as continuouslyexposing more surface area to chemical attack, raising the localtemperature (which increases the dissolution rate) by the frictionbetween the particles and the metal and enhancing the diffusion ofreactants and products to and away from the surface by mixing and byreducing the thickness of the boundary layer.

The slurry composition is an important factor in the CMP step. Dependingon the choice of the oxidizing agent, the abrasive, and other usefuladditives, the polishing slurry can be tailored to provide effectivepolishing of metal layers at desired polishing rates while minimizingsurface imperfections, defects, corrosion, and erosion of oxide in areaswith tungsten vias. Furthermore, the polishing slurry may be used toprovide controlled polishing selectivities to other thin-film materialsused in current integrated circuit technology such as titanium, titaniumnitride and the like.

There is a significant need for metal CMP process(es) and slurry(s) thatafford low dishing and plug recess effects especially in view of thefact that the semiconductor industry continues to move towards smallerand smaller feature sizes. The present invention provides a solution tothis significant need.

BRIEF SUMMARY OF THE INVENTION

In an embodiment, the invention is a combination of a chemicalmechanical polishing composition in contact with a substrate surfacehaving at least one feature thereon comprising tungsten, saidcombination comprising:

a) a substrate comprising submicron integrated circuits and having asurface having at least one feature thereon comprising tungsten, saidsubstrate surface contacting a chemical mechanical polishing compositioncomprising;

b) periodic acid; and

c) an abrasive;

wherein said periodic acid and said abrasive are present in a combinedamount sufficient to render the substrate surface substantially planarand to maintain a removal rate of tungsten of at least 800 Angstroms perminute upon chemical-mechanical polishing thereof when polishing is doneat 4 pounds per square inch (psi) of down force. In an embodiment, thesurface of the substrate also has at least one feature thereoncomprising a dielectric material.

In another embodiment, the invention is a method for chemical mechanicalpolishing of a surface having at least one feature thereon comprisingtungsten, said method comprising the steps of:

-   A) placing a substrate having the surface having the at least one    feature thereon comprising tungsten in contact with a polishing pad;-   B) delivering a polishing composition comprising:

a) an abrasive;

b) periodic acid; and

-   C) polishing the substrate with the polishing composition.

DETAILED DESCRIPTION OF THE INVENTION

This invention involves a combination, a slurry and an associated methodfor chemical mechanical planarization of a tungsten-containingsubstrate. The combination is that of a chemical mechanical polishingcomposition in contact with a substrate surface having at least onefeature thereon comprising tungsten. Minimization or prevention ofdishing/erosion and plug recess of features on semiconductor substratesduring CMP processing is becoming increasingly more important as thesemiconductor industry trends to smaller and smaller feature sizes inthe manufacture of integrated circuits.

The tungsten CMP slurry composition and combination described hereinsatisfies the need for low selectivity of tungsten removal rates todielectric removal rates. The general composition consists of anabrasive, periodic acid as oxidizer, and, in some embodiments, achelator. By varying the ratio of abrasive to oxidizer, both removalrates and selectivity can be tuned to those desired for a specificapplication. Addition of an appropriate chelator provides for both pHadjustment and stability with regard to pH drift. The chelator alsodecreases cost of ownership by boosting tungsten removal rate andthereby reducing the amount of oxidizer needed for a given tungstenremoval rate to be obtained.

In this invention, the oxidizer is periodic acid (PIA). The level ofperiodic acid in the slurry can range from about 0.1 weight percent toabout 15 weight percent, and, for example can range from about 0.1weight percent to about 5 weight percent. In an embodiment, the periodicacid ranges from about 0.2 weight percent to about 5 weight percent. Inanother embodiment, the periodic acid ranges from about 0.5 to about 2weight percent.

Suitable abrasives for this invention include, but are not limited to,alumina, ceria, germania, silica, titania, zirconia, and mixturesthereof. In one embodiment, the abrasive is silica (colloidal silica orfumed silica). In an embodiment, the abrasive is colloidal silica. Theabrasive level in the slurry can broadly range from about 0.1 weightpercent to about 25 weight percent of the total weight of the slurryand, for example, can range from about 0.1 weight percent to about 15weight percent. In an embodiment, the abrasive level ranges from about 2weight percent to about 15 weight percent, and, in another embodiment,ranges from about 4 weight percent to about 14 weight percent, forexample, from about 5 weight percent to about 13 weight percent. In apreferred embodiment, the abrasive level ranges from about 5 weightpercent to about 13 weight percent.

In a preferred embodiment, the periodic acid level ranges from about 0.9weight percent to about 2 weight percent in a slurry, where the abrasivelevel ranges from about 5 weight percent to about 13 weight percent. Asshown in the examples, such a slurry has been found to possess lowtungsten:dielectric (specifically W:TEOS) selectivity values which rangefrom about 0.73 to about 1.12 that vary with the amount of periodic acidin relation to the amount of abrasive (e.g., colloidal silica).

In some embodiments, the composition and combination are furthercomprised of an amino-alcohol compound that serves a dual function ofbeing a chelator as well as being a pH-adjusting agent that serves toincrease pH of the resulting composition.

Furthermore, the amino-alcohol compound is also a stabilizer. Thechelating function is beneficial in boosting metal removal rates duringCMP processing and the basic properties of the amino-alcohol compoundare useful in increasing pH values of periodic acid-based slurries,which are highly acidic. Raising slurry pH values from around 1-2 to 3or higher is highly desirable commercially in reducing or eliminatingpotential corrosion and safety problems associated with such very low pHslurries. Surprisingly and unexpectedly, an amino-alcohol compound suchas 2-(2-aminoethoxy)ethanol has been found to impart long slurrystability and lifetime with respect to pH drift when this component ispresent in a slurry. As shown in the examples, an inventive periodicacid-based slurry maintained virtually constant pH of ˜3.5 over manymonths with 2-(2-aminoethoxy)ethanol being present in the slurry. In anembodiment, the amino-alcohol compound is selected from the groupconsisting of 2-(2-aminoethoxy)ethanol, 2-(2-aminoethylamino)ethanol,diethanolamine, ethanolamine, and triethanolamine. In an embodiment, theamino-alcohol compound is 2-(2-aminoethoxy)ethanol.

If present, the level of the amino-alcohol compound can range from about0.1 weight percent to about 5 weight percent. In an embodiment, thelevel ranges from about 0.1 weight percent to about 2 weight percent,and, in another embodiment, the level ranges from about 0.1 weightpercent to about 1 weight percent. In an embodiment, an amino-alcoholcompound is present in the composition and combination and the pH rangesfrom about pH 1 to about pH 4. In another embodiment, an amino-alcoholcompound is present in the composition and combination and the pH rangesfrom about pH 5 to about pH 10.

Other chemicals that may be added to the CMP slurry composition include,for example, surfactants, pH-adjusting agents, acids, corrosioninhibitors, fluorine-containing compounds, chelating agents,nitrogen-containing compounds, and salts.

Suitable surfactant compounds that may be added to the slurrycomposition include, for example, any of the numerous nonionic, anionic,cationic or amphoteric surfactants known to those skilled in the art.The surfactant compounds may be present in the slurry composition in aconcentration of about 0 weight % to about 1 weight % and, when present,are preferably present in a concentration of about 0.001 weight % toabout 0.1 weight % of the total weight of the slurry. The preferredtypes of surfactants are nonionic, anionic, or mixtures thereof and aremost preferably present in a concentration of about 10 ppm to about 1000ppm of the total weight of the slurry. A suitable nonionic surfactant isSurfynol® 104E, which is a 50:50 mixture by weight of2,4,7,9-tetramethyl-5-decyn-4,7-diol and ethylene glycol (solvent), (AirProducts and Chemicals, Inc., Allentown, Pa.). Suitable anionicsurfactants include cetyl trimethylammonium bromide and ammonium laurylsulfate.

An (initial or additional) pH-adjusting agent may be used to improve thestability of the polishing composition, to improve the safety inhandling and use, or to meet the requirements of various regulations.Suitable pH-adjusting agents or additional pH-adjusting agents to lowerthe pH of the polishing composition of the present invention include,but are not limited to, hydrochloric acid, nitric acid, sulfuric acid,chloroacetic acid, tartaric acid, succinic acid, citric acid, malicacid, malonic acid, various fatty acids, various polycarboxylic acidsand mixtures thereof. Suitable pH-adjusting agents or additionalpH-adjusting agents to raise the pH of the polishing composition of thepresent invention include, but are not limited to, potassium hydroxide,sodium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide,ethylenediamine, piperazine, polyethyleneimine, modifiedpolyethyleneimines, and mixtures thereof.

Suitable acid compounds that may be added to the slurry compositioninclude, but are not limited to, formic acid, acetic acid, propanoicacid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid,octanoic acid, nonanoic acid, lactic acid, hydrochloric acid, nitricacid, phosphoric acid, sulfuric acid, hydrofluoric acid, malic acid,tartaric acid, gluconic acid, citric acid, phthalic acid, pyrocatechoicacid, pyrogallol carboxylic acid, gallic acid, tannic acid, and mixturesthereof. These acid compounds may be present in the slurry compositionin a concentration of about 0 weight % to about 1 weight % of the totalweight of the slurry.

Suitable (initial or additional) chelating agents that may be added tothe slurry composition include, but are not limited to,ethylenediaminetetracetic acid (EDTA),N-hydroxyethylethylenediaminetriacetic acid (NHEDTA), nitrilotriaceticacid (NTA), diethylenetriaminepentacetic acid (DPTA),ethanoldiglycinate, tricine, 2,2′-bipyridyl, tartaric acid, glutamicacid, aspartic acid, glutamine, L-aspartic acid, L-tryptophan,L-asparagine, L-arginine and mixtures thereof. The chelating agents maybe present in the slurry composition in a concentration of about 0weight % to about 3 weight %, and are preferably present in aconcentration of about 0.05 weight % to about 0.20 weight % of the totalweight of the slurry

Suitable nitrogen-containing compounds that may be added to the slurrycomposition include, but are not limited to, ammonium hydroxide,hydroxylamine, monoethanolamine, diethanolamine, triethanolamine,diethyleneglycolamine, N-hydroxylethylpiperazine, polyethyleneimine,modified polyethyleneimines, and mixtures thereof. Suitablenitrogen-containing compounds also include various amino acids. Suitableamino acids include, but are not limited to, alanine, arginine,asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine,histidine, isoleucine, leucine, lysine, methionine, phenylalanine,proline, serine, threonine, tryptophan, tyrosine, and valine. In anembodiment, the amino acid is glycine. The nitrogen-containing compoundsmay be present in the slurry composition in a concentration of about 0weight % to about 1 weight %, and are preferably present in aconcentration of about 0.01 weight % to about 0.20 weight % of the totalweight of the slurry.

Suitable salts that may be added to the slurry composition include, butare not limited to, ammonium persulfate, potassium persulfate, potassiumsulfite, potassium carbonate, ammonium nitrate, potassium hydrogenphthalate, hydroxylamine sulfate, and mixtures thereof. The salts may bepresent in the slurry composition in a concentration of about 0 weight %to about 10 weight %, and are preferably present in a concentration ofabout 0 weight % to about 5 weight % of the total weight of the slurry.A preferred salt is ammonium nitrate and is most preferably present in aconcentration of about 0 weight % to about 0.15 weight % of the totalweight of the slurry.

Still other chemicals that can be added to the slurry compositions arebiological agents such as bactericides, biocides and fungicidesespecially if the pH is around about 6 to 9. Suitable biocides, include,but are not limited to, 1,2-benzisothiazolin-3-one;2(hydroxymethyl)amino ethanol; 1,3-dihydroxymethyl-5,5dimethylhydantoin;1-hydroxymethyl-5,5-dimethylhydantion; 3-iodo-2-propynyl butylcarbamate;glutaraldehyde; 1,2-dibromo-2,4-dicyanobutane;5-chloro-2-methyl-4-isothiazoline-3-one; 2-methyl-4-isothiazolin-3-one;and mixtures thereof.

The slurry compositions and associated methods of this invention canhave pH values that broadly range from about 1 to about 11 andpreferably range from about 1.5 to about 5, such as from about 2 toabout 4. In an embodiment, the pH ranges from about 2 to about 4; inanother embodiment, the pH ranges from about 5 to about 10. In manyapplications of this invention, such as for tungsten CMP, a pH value inthe range from about 2 to about 4 is preferred. Having a pH below 2 canraise concerns about safety and corrosion incidents occurring at theselow pH values. Having a pH above about 4 for tungsten CMP can result insignificantly reduced tungsten removal rates and may destabilize thecolloidal silica.

Associated Method

The associated method of this invention entails use of theaforementioned composition (as disclosed supra) for chemical mechanicalplanarization of substrates comprised of metals and dielectricmaterials. In the methods, a substrate (e.g., a wafer) is placedface-down on a polishing pad which is fixedly attached to a rotatableplaten of a CMP polisher. In this manner, the substrate to be polishedand planarized is placed in direct contact with the polishing pad. Awafer carrier system or polishing head is used to hold the substrate inplace and to apply a downward pressure against the backside of thesubstrate during CMP processing while the platen and the substrate arerotated. The polishing composition (slurry) is applied (usuallycontinuously) on the pad during CMP processing to effect the removal ofmaterial to planarize the substrate.

In the combination and associated method of the invention, a removalrate of tungsten of at least 800 Angstroms per minute is maintained uponchemical-mechanical polishing thereof when polishing is done at 4 psi ofdown force. Higher removal rates are attained when down force valuesgreater than 4 psi are used. In an embodiment, the removal rate oftungsten is at least 1000 Angstroms per minute. In other embodiments,the removal rates of tungsten are at least 1200 Angstroms per minute,1500 Angstroms per minute, and 2000 Angstroms per minute.

As indicated above, an embodiment of the invention is a combination of achemical mechanical polishing composition in contact with a surface of asubstrate having at least one feature thereon comprising tungsten. In anembodiment, the surface of the substrate also has at least one featurethereon comprising a dielectric material. In an embodiment, thedielectric material is a silicon oxide.

In embodiments of the combination and method according to the invention,a tunable tungsten/dielectric selectivity is realized uponchemical-mechanical polishing the substrate using the composition, whichselectivity depends upon the amount of abrasive in relation to theamount of periodic acid. In embodiments of the combination and methodaccording to the invention, the tungsten/dielectric selectivity rangesfrom about 0.5 to about 1.5 in one case, ranges from about 0.7 to about1.3 in another case, and ranges from about 0.8 to about 1.2 in yetanother case.

The present invention is further demonstrated by the examples below.

EXAMPLES General

All percentages are weight percentages unless otherwise indicated.

CMP Methodology

In the examples presented below, CMP experiments were run using theprocedures and experimental conditions given below.

Glossary

Components

-   Polishing Pad, Politex®, and IC1000 were used during CMP, supplied    by Rohm & Haas, Inc.    Parameters

General

-   Å: angstrom(s)—a unit of length-   BP: back pressure, in psi units-   CMP: chemical mechanical planarization=chemical mechanical polishing-   CS: carrier speed-   DF: Down force: pressure applied during CMP, units psi-   min: minute(s)-   ml: milliliter(s)-   mV: millivolt(s)-   psi: pounds per square inch-   PS: platen rotational speed of polishing tool, in rpm (revolution(s)    per minute)-   SF: slurry flow, ml/min-   TEOS: tetraethylorthosilicate-   wt. %: weight percentage (of a listed component).-   W:TEOS Selectivity: removal rate of W/removal rate of TEOS.    Removal Rates:

Tungsten Removal Rates: Measured tungsten removal rate at 4.0 psi downpressure of the CMP tool.

CMP Methodology:

In the examples presented below, CMP experiments were run using theprocedures and experimental conditions given below.

Metrology:

Tungsten films were measured with a ResMap CDE, model 168, manufacturedby Creative Design Engineering, Inc, 20565 Alves Dr., Cupertino, Calif.,95014. The ResMap tool is a four point probe sheet resistance tool.Forty nine point diameter scan at 5 mm edge exclusion for Tungsten filmwas taken.

CMP Tool:

The CMP tool that was used is a Mirra, manufactured by AppliedMaterials, 3050 Boweres Avenue, Santa Clara, Calif., 95054. A IC1000,kgroove stacked on a suba IV pad supplied by Rohm & Haas, Inc, 451Bellevue Rd., Newark, Del. 19713, was used on platen 1 for blanket andpattern wafer studies. On Platen 3 a Politex pad, supplied by Rohm &Haas was used for the TEOS defect wafers after polishing on platen 1.

The IC1000 pad was broken in by conditioning the pad for 18 minutes at 7lbs down-force on the conditioner. The Politex pad was broken in bypolishing twenty TEOS dummy wafers with De-ionized water. In order toqualify the tool settings and the pad break-in two Tungsten monitors andtwo TEOS monitors were polished with Microplanar® CMP3850, supplied byDuPont Air Products NanoMaterials L.L.C. at baseline conditions.

In blanket wafer studies, tungsten blanket wafers were polished atbaseline conditions. The tool baseline conditions were: table speed; 120rpm, head speed: 123 rpm, membrane pressure; 4.0 psi, inter-tubepressure; 5.0 psi, retaining ring pressure; 6.5 psi, slurry flow; 150ml/min.

Wafers:

Polishing experiments were conducted using CVD deposited Tungstenwafers. These blanket wafers were purchased from Silicon ValleyMicroelectronics, 2985 Kifer Rd., Santa Clara, Calif. 95051. The filmthickness specifications are summarized below: W: 8,000 Å CVD tungsten,240 Å TiN, 5000 Å TEOS on silicon.

Examples 1-12

Slurry samples of batch size 3 kg were made having the weight percentcompositions as shown in Table 1 (with water being a third componentthat is the balance of the composition in each case). The samples eachcontained colloidal silica, periodic acid, and deionized water. Thecolloidal silica was MicroPlanar® CMP3850 supplied by DuPont AirProducts NanoMaterials, L.L.C., 2441 W. Erie Dr., Tempe, Ariz. 85282 andhad a pH of ˜3 as supplied. The periodic acid was also obtained fromDuPont Air Products NanoMaterials, L.L.C.

CMP experiments were conducted using tungsten and TEOS blanket wafers onthe Mirra tool with the following conditions being used for all samples:down-force of 4.0 psi, slurry flow rate of 150cc/min, and tablerotational speed of 120 rpm. Removal rates for both tungsten and TEOSwere measured at 4 psi down-force for the polishing tool. These arereported in Table 1 and were used to calculate the W:TEOS selectivityvalues reported in Table 1.

The compositions and results obtained for samples 1-12 (corresponding toExamples 1-12) are summarized in Table 1. The results obtaineddemonstrate that these slurries are tunable with respect totungsten/TEOS selectivity by variation of the ratio of the amount ofcolloidal silica to the amount of periodic acid. The W:TEOS selectivityincreases with increasing periodic acid level and decreasing colloidalsilica level.

TABLE 1 Examples of Low-selective Tungsten Formulations: Tunability ofW:TEOS Selectivity Sample Composition#/ Example Example Example ExampleProperties 1 2 3 4 Colloidal Silica (wt %) 13 9 5 11 PIA (wt %) 0.5 0.50.5 0.9 pH before PIA 2.99 3.17 3.38 3.07 pH after PIA 1.92 1.97 1.971.79 Removal rates* of W 1114 1017 883 1379 at 4 psi, 60 sec Removalrates* of 2081 1619 1274 1894 TEOS at 4 psi, 60 sec W:TEOS Selectivity0.54 0.63 0.69 0.73 Example Example Example Example 5 6 7 8 ColloidalSilica (wt %) 13 7 11 13 PIA (wt %) 1.25 0.9 1.6 2 pH before PIA 2.933.32 2.95 2.87 pH after PIA 1.73 1.74 1.61 1.58 Removal rates* of W 16921341 1745 2115 at 4 psi, 60 sec Removal rates* of 2162 1484 1925 2174TEOS at 4 psi, 60 sec W:TEOS Selectivity 0.78 0.90 0.91 0.97 ExampleExample Example Example 9 10 11 12 Colloidal Silica (wt %) 7 9 5 5 PIA(wt %) 1.6 2 1.25 2 pH before PIA 3.16 3.07 NA 3.31 pH after PIA 1.611.63 1.73 1.60 Removal rates* of W 1635 1861 1475 1712 at 4 psi, 60 secRemoval rates* of 1526 1718 1320 1321 TEOS at 4 psi, 60 sec W:TEOSSelectivity 1.07 1.08 1.12 1.30 *All removal rates reported are in unitsof angstroms/minute of polishing time. #Water is the balance for eachcomposition in this table.

Example 13

A slurry of batch size 3 kg was made up that contained 10 weight percentcolloidal silica, 1.11 weight percent of periodic acid, and water(balance of this composition). This slurry was used in polishingexperiments on patterned wafers of different arrays (as reported inTable 2). Erosion values incurred during polishing of the differentwafers measured at center, middle, and edge die positions weredetermined as reported in Table 2 for three different levels ofover-polish (OP): (15%, 30%, and 60%). The results demonstrated thatthere was little change in the extent of erosion incurred duringpolishing with use of this slurry at increasing levels of over-polish upto 60%, which is highly desirable.

TABLE 2 Examples of Low-selective Tungsten Formulations: Erosion vs.overpolish Example Example Example 13 13 13 15% OP 30% OP 60% OPColloidal Silica (wt %) 10 10 10 PIA (wt %) 1.11 1.11 1.11 Erosion at 2× 3 arrays (0.24 um contact space within array, 0.16 um contact) Centerdie 47 57 75 Middle die 21 47 79 Edge die 23 50 75 Erosion at 3 × 3arrays (0.20 um contact space within array, 0.16 um contact) Center die43 89 75 Middle die 26 57 78 Edge die 37 57 92 Erosion at 3 × 3 arrays(0.16 um contact space within the array, 0.16 um contact) Center die 3866 75 Middle die 43 81 78 Edge die 40 61 110 Erosion at 0.15 μm contactarray, 5.1% density Center die 14 29 49 Middle die 11 31 40 Edge die 1023 37

Examples 14 AND 15

In these examples, the effect of 2-(2-aminoethoxy)ethanol as both achelator and pH adjustor was demonstrated. Two samples were made asshown in Table 3 with both containing PIA at 1.25 weight percent andcolloidal silica at 9 weight percent. The sample for Example 14 did notcontain any 2-(2-aminoethoxy)ethanol, while the sample for Example 15contained this component at a level of 0.582 weight percent. Thecomparative results obtained are shown in Table 3 and are dramatic inthat having this chelator/pH adjustor present boosted the tungstenremoval rate significantly, while also raising the final pH nearly 2 pHunits to approximately 3.5 (which pH value is highly desirable over thelower pH of Example 14 of 1.59 with respect to corrosion and safetyconcerns at the lower pH).

TABLE 3 Examples of Low-selective Tungsten Formulations: Effect ofChelator Example Example 14 15 Colloidal Silica (wt %) 9 92-(2-aminoethoxy)ethanol 0 0.582 PIA (wt %) 1.25 1.25 pH before PIA 3.0410.45 pH after PIA 1.59 3.48 Removal rates* of W 1587 2120 at 4 psi, 60sec Removal rates* of 1714 1601 TEOS at 4 psi, 60 sec W:TEOS Selectivity0.93 1.32 *All removal rates reported are in units of angstoms/minute ofpolishing time.

Examples 16-18

In these examples, two PIA/colloidal silica slurries were prepared withand without 2-(2-aminoethoxy)ethanol being present, as shown in Table 4.Example 16 did not contain this component, while Example 17 did containthis component. Also in Example 18 a PIA/colloidal silica slurry wasprepared using ammonium hydroxide in place of 2-(2-aminoethoxy)ethanol.The pH of these slurries was monitored over 7 months, as shown in Table4. The results demonstrated essentially a constant pH was maintained inthe Example 17 slurry containing 2-(2-aminoethoxy)ethanol as pHadjustor/chelator as well as in the Example 16 slurry without thisadditive. In sharp contrast, significant pH variations were found tooccur in the Example 18 slurry having ammonium hydroxide in place of2-(2-aminoethoxy)ethanol. Similar results to the Example 18 slurry wereobtained using potassium hydroxide in place of ammonium hydroxide.

TABLE 4 pH Stability Data^(a): Effect of Chelator Time 0 1 2 3 7 monthmonth months months months Example 16 1.68 1.67 1.72 1.71 1.79 Example17 3.48 3.62 3.70 3.74 3.59 Example 18 6.14 2.51 monitoring discontinueddue (Comparative) to high shift in pH ^(a)Table shows pH value of eachsample measured soon after preparation (0 month), 1 month, 2 months, 3months, and 7 months after preparation of the sample.

The invention claimed is:
 1. A method for chemical mechanical polishingof a surface having at least one feature thereon comprising tungsten andat least one feature thereon comprising a dielectric material, saidmethod comprising the steps of: a. placing a substrate having thesurface in contact with a polishing pad; b. delivering a polishingcomposition comprising: an abrasive; periodic acid; and an amino alcoholcompound; and c. polishing the substrate with the polishing compositionwherein said periodic acid and said abrasive are present in a combinedamount sufficient to render the substrate surface substantially planarand to maintain a removal rate of tungsten of at least 800 Angstroms perminute upon chemical-mechanical polishing thereof when polishing is doneat 4 psi of down force ; and a tunable tungsten/dielectric selectivityranging from 0.5 to 1.5 is realized upon chemical-mechanical polishingthe substrate using the composition.
 2. The method of claim 1, whereinthe dielectric material is a silicon oxide.
 3. The method of claim 1,wherein the amino-alcohol compound is selected from the group consistingof 2-(2-aminoethoxy)ethanol, 2-(2-aminoethylamino)ethanol,diethanolamine, ethanolamine, triethanolamine and mixtures thereof. 4.The method of claim 3, wherein the amino-alcohol compound is2-(2-aminoethoxy)ethanol.
 5. The method of claim 1, further comprising apH-adjusting agent, wherein the composition has a pH ranging from pH 1to pH
 4. 6. The method of claim 1, wherein the periodic acid is presentin an amount from 0.1 weight percent to 5 weight percent.
 7. The methodof claim 1, wherein the abrasive is present in an amount from 0.1 to 15weight percent.
 8. The method of claim 1, wherein the tunabletungsten/dielectric selectivity depends upon the amount of abrasive inrelation to the amount of periodic acid.